Side-channel blowers or pumps have previously been described. In a vehicle, they serve, for example, to convey fuel, to blow secondary air into the exhaust system, or to convey hydrogen for PEM fuel cell systems. The drive is usually effected by an electric motor whose output shaft has the impeller arranged thereon. Side-channel blowers have previously been described in which only one flow channel is formed on an axial side of the impeller in a housing part, as well as side-channel blowers formed with a flow channel on either axial side of the impeller, in which case both flow channels are in fluid communication with each other. In such a side-channel blower, one of the flow channels is most often formed in a housing part which serves as a cover, while the other flow channel is formed in the housing part to which the drive unit is typically mounted, on the shaft of which the impeller is arranged to rotate therewith. The impeller is designed at its periphery so that it forms one or two circumferential vortex ducts together with the flow channel or the flow channels surrounding the impeller.
In side-channel blowers with two axially opposite vortex ducts, the impeller blades are divided axially across a radial section into two sections which are respectively assigned to the opposite flow channel. Pockets are formed between the impeller blades, in which, when the impeller rotates, the fluid conveyed is accelerated by the impeller blades in the circumferential direction, as well as in the radial direction so that a circulating vortex flow is generated in the flow channel. With impeller blades of a radially open design, an overflow from one flow channel to the other most often occurs via the gap between the radial end of the impeller and the radially opposite side wall.
In order to obtain the best possible conveyance or pressure increase, different measures have been taken in conveying gases and liquids which are due to the different behavior of compressible and incompressible or slightly compressible media when they are conveyed.
The generation of noise should be taken into account when conveying in side-channel blowers since acoustically disturbing pressure surges occur at the beginning of the interruption zone immediately after a medium has flowed over each impeller blade because compressed gas is still present in the pockets between the impeller blades, which gas has not been completely expelled via the outlet and is suddenly accelerated against the walls of the interruption zone when it reaches that zone. This causes significantly increased noise emissions.
U.S. Pat. No. 6,422,808 B1 describes a side-channel blower for a compressible fluid to increase conveying pressure comprising an impeller enclosed by a flow housing with two side channels, the flow housing having a fluid inlet and a fluid outlet. Blades are arranged along the periphery of the impeller that extend in an axial and a radial direction and which have a radially inner section inclined oppositely to the direction of rotation of the rotor, as well as a radial outer section inclined in the direction of rotation of the rotor, and which convey fluid from the inlet to the outlet as the rotor rotates. The blades each have a chamfer at the radially inner section.
A side-channel blower is also described in U.S. Pat. No. 5,299,908 B1 whose impeller blades extend straightly in a radial direction, but are inclined towards the opposite side channel with respect to the direction of rotation. A radial partition wall is, however, arranged between these two axial blade parts to prevent an overflow from one duct to the other via the impeller. Only a radially outer part of the blades is further formed opposite the flow channel.
Blades that are inclined and separated from each other in such a manner have also been previously described from an impeller of a side-channel pump for an incompressible medium. This impeller also has a radially limiting side wall.
All these blowers and pumps are not, however, optimal in view of their feed rate and in view of the possible pressure increase, respectively.